Getting in and outa Dodge

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The Port of Miami seaport is located on Dodge Island in the waters of Biscayne Bay in the City of Miami. It is the busiest passenger cruise seaport in the world, having handled over four million passengers in each of the past four calendar years. It’s currently the 11th largest cargo container port in the United States, and the goal is to increase its cargo handling capacity with a trio of infrastructure projects at the Port of Miami: 1) Restoration of rail service between Dodge Island and the Florida East Coast rail yards, which will connect the Port of Miami with the system of railroads in the United States; 2) dredging the channel adjacent to Dodge Island in order to accommodate the larger cargo ships which will be passing through the Panama Canal, after the Panama Canal is expanded in 2014; and, the subject of this article, 3) the construction of a new highway through two parallel tunnels passing beneath the channel of water separating Dodge Island from nearby Watson Island. This pair of highway tunnels is called the Port of Miami Tunnel, and the tunnels are being dug by Bouygues Civil Works Florida (BCWF), a subsidiary of the French firm Bouygues Travaux Publics.

Currently, all vehicle traffic to and from the seaport on Dodge Island must pass through the downtown streets of the City of Miami. When finished, the Port of Miami Tunnel will allow this traffic to bypass downtown streets by connecting Dodge Island directly to Interstate 395 on Watson Island, relieving congestion on the City streets. Tunnel digging operations began in November of 2011, and the project is scheduled to be completed in May of 2014. Each of the two tunnels going beneath the shipping channel will be more than 4,000 feet long. In support of the tunnel, additional lanes are also being constructed on the Interstate 395 bridge between the mainland and Watson Island to handle the vehicle traffic to and from the Port of Miami Tunnel. The total cost to construct the Port of Miami Tunnel is expected to be approximately $1 billion.

When slightly more than 700 feet of the first tunnel had been dug, a group of 20 students, faculty, staff, and industry advisors from the Geomatics Engineering program at Florida Atlantic University (FAU) were invited to tour the project site by BCWF. Since the surveying engineering operations of the site were of primary interest to this group of visitors, the tour was appropriately hosted by coauthors Mael Le Coq, Chief Tunnel Surveyor for BCWF, and Robert Loane, Tunnel Surveyor for BCWF and a 2011 graduate of the FAU Geomatics Engineering program. Mael and Rob showed the group the construction site and educated the visitors about their activities, which are crucial to successful completion of the project.

At the current stage of construction, the surveyors for BCWF are constantly busy with several important tasks which keep the tunnel boring operations on schedule. Much of their activity is devoted to guiding the tunnel boring machine (TBM) as it digs along the design path of the tunnel. The TBM, from the front of the 43-foot diameter, 265 ton cutter head to the end of the rearmost of six gantries, is 457 feet long. The $45 million TBM was custom designed and built for this project, and will employ several different means of digging through the sand and limestone strata expected to be encountered. Electric motors spin the cutter head at 4 RPM during digging operations. Hydraulic cylinders behind the cutter head provide thrust and enable steering of the TBM by means of pushing against the concrete tunnel liner which is constructed behind the cutter head as it progresses along its path.

One of the particularities of this tunnel project is that on both Dodge and Watson islands, the TBM starts the boring operations below mean sea level. To do this, two 400 foot long, 100 foot wide, and 40 foot deep boxes were excavated, one on each island. A waterproof lining made with the help of a cement and bentonite grout forms the walls of the boxes, but the boxes nevertheless filled with infiltrating seawater as they were excavated. Excavation was closely monitored by the BCWF surveyors using echo sounders in barges in order to make sure the theoretical grade of the bottom of the boxes was reached. When excavation of each box was completed, a thick tremie slab was poured on the bottom to make the entire box waterproof, and the seawater was then pumped out so that tunnel boring could commence at the end of the box.

TBM guidance occurs in real time during production. Every seven seconds, the current position of the cutter head is updated and displayed on two touchscreen panels in the closet-size TBM control room, which is situated immediately behind the cutter head. TBM position updates are provided by a Topcon QS1A total station, together with tilt sensors on the TBM. The total station is mounted to a bracket anchored to the ceiling of the tunnel and measures angles and distances between backsight targets on control stations and a target on the cutter head. The QS1A is controlled via wireless network from the control room. TBM positioning software called Pyxis was developed in-house at Bouygues specifically for their tunnel boring operations. By displaying the current position and orientation of the TBM with respect to the design location of the tunnel, the pilot of the TBM knows what direction to steer the machine in order to keep it boring along the desired path.

During production, the concrete liner of the tunnel mentioned above is constructed by placing precast concrete ring segments against the freshly dug tunnel walls immediately behind the cutter head. Grout is injected behind the rings after placement. The concrete liner deforms after the segments are placed, and the tunnel surveyors document the amount of deformation and the final position of the rings by making measurements of the cross section of the tunnel using Leica total stations and the on-board TMS ProScan software developed by Amberg Technologies. The as-built center of each completed ring must be within 4 inches of the design tunnel alignment.

Control points in the tunnel are provided by a traverse starting from control points on the surface and carried into the tunnel by means of brackets mounted to the concrete liner. Targets and instrumentation are mounted to these brackets as needed. Traverse measurements have to be performed with the highest accuracy in order to ensure correct guidance of the TBM, particularly since GPS is unavailable in the tunnel and additional control points are not available until breakthrough of the TBM at the far end of the tunnel.

Many additional operations are performed by Mael, Rob, and the other surveyors for Bouygues. They are responsible for the staking out of various facilities at the construction site, which are interwoven with Interstate 395 and other facilities on Watson Island. The surveyors have set out or measured the locations of 800 grout injection boreholes at the project site, which are needed to stabilize the soil which lies in the path of the TBM. Differential leveling done to monitor ground subsidence in the vicinity of the tunnel occurs at regular intervals of time. For these operations, a variety of hardware and software are employed. Total stations used for the control surveys, layout, and as-built survey purposes include the QS1A mentioned earlier, the Leica TCRA1201+, and the Leica TS15 with a CS10 controller. Leica DNA03 and Leica Sprinter 200M digital levels are used for elevation determination. The GPS system used by BCWF surveyors is the Topcon PG-1A with the GRS1 controller. In addition to Pyxis software used for TBM guidance, software used for BCWF’s positioning activities include
Autocad 2011, Leica Viva, Leica Geo Office, Topcon TopSURV, Amberg TMS Office, Amberg TMS ProScan, Geomedia Covadis, and Microsoft Office.

One of the difficulties BCWF surveyors are experiencing on a daily basis is working with different units. Dimensions in the drawings are given in feet and inches, coordinates are expressed in feet, and the guidance system works in meters. American colleagues ask for results in feet while colleagues from other countries prefer meters.

The Port of Miami Tunnel construction project requires a significant amount of surveying engineering activities in support of the tunnel boring activities. One of the visitors from the FAU group observed that nearly every activity on that construction site was essentially geared toward keeping the pilot of that TBM digging productively, 20 hours per day, 7 days per week. As with any other high-dollar construction project needing surveyors, production will not take place without the tunnel surveyors of BCWF keeping track of every aspect of the project which requires spatial position data.

The students, faculty and advisors of the Geomatics Engineering program at Florida Atlantic University wish to thank Louis Brais, Project Director, Pierre Pascual, Tunnel Construction Director, and Bernard Catalano, Tunnel Construction Manager, for providing the opportunity for a memorable visit to the Port of Miami Tunnel.

Loren J. Gibson is an Instructor in the Geomatics Engineering program at Florida Atlantic University. Loren is licensed to practice surveying and mapping in the states of Florida and New York. He received his MS degree in Computational Science from the State University of New York, College at Brockport.

Mael Le Coq is Chief Surveyor in charge of the tunnel survey works on the Port Of Miami Tunnel project for Bouygues Civil Works Florida. He has a Masters Degree in Survey Engineering from the ESTP in Paris, France and a Master of Science in Environmental Management and Earth Observation from the University of Nottingham, United Kingdom. He has five years of experience mainly in tunnel surveying working for Bouygues Travaux Publics on the A41 highway project in France, Gautrain project in South Africa and the Port Of Miami Tunnel project in USA.

Robert Loane is a Tunnel Surveyor, in charge of taking field measurements, tunnel guidance, data processing, and producing CAD drawings. He has a BS in Geomatics Engineering from FAU, AA and AS from Indian River State College, is ESRI GIS certified, and has been a multiple scholarship award winner. He has 5 years surveying experience.

A 2.584Mb PDF of this article as it appeared in the magazine—complete with images—is available by clicking HERE